An international mobile subscriber identity (IMSI for short) is a symbol for distinguishing between mobile subscribers, stored in a subscriber identity module (SIM for short) card or a universal subscriber identity module (USIM for short) card, and used to identify a mobile subscriber.
In the prior art, when a terminal device accesses a wireless network, first, an IMSI needs to be allocated to the terminal device, so that a network side device correctly identifies the terminal device accessing the wireless network. An IMSI of each terminal device needs to be unique in the whole network and in a global range.
However, each terminal device owns a globally unique IMSI. The IMSI includes a 5-bit public land mobile network (PLMN for short) and a 10-bit mobile subscriber identification number (MSIN for short). The PLMN is used to indicate a different mobile communications operator in a country or a region. The MSIN is used to indicate a mobile subscriber identification number. Therefore, theoretically, only 10 billion terminal devices can be identified in one mobile network. With development of mobile communications networks, machine to machine (M2M for short) communication increases, inevitably resulting in IMSI resource depletion.